The number of books available in ever growing Family History Archive increased by over 600 in last two days to a total of 28,342. Although this number of books is only a very small percentage of the total volumes available in libraries around the country, this is the first time that access to this number of genealogy specific books has been free on the Internet.
Other large collections of digitized books are available from Ancestry.com but access is subject obtaining a subscription or visiting one of the libraries or Family History Centers that have free public access.
Google Books also has a huge catalogue of digitized books including thousands of books relevant to genealogical research. However, not all the books that show up in a Google Books search are actually digitized and online. Most of the books are merely cataloged and possibly available for sale. Project Gutenberg also has a very large selection of digitized books, but only relatively a few are related to genealogy or family history.